What does humidity measure?

Humidity specifically measures the quantity of water vapor present in the air. It is an important factor in meteorology because it influences weather patterns, precipitation, and overall atmospheric conditions. There are various ways to express humidity, including absolute humidity, relative humidity, and specific humidity, but all forms convey the idea of how much moisture is contained in the air at a given temperature.

Understanding humidity is crucial for various applications, including forecasting weather and studying climate change, as high humidity can lead to discomfort in humans and can also affect storm development.

The other choices relate to different aspects of meteorological study. Wind speed is a measure of how fast air is moving in the atmosphere, cloud density refers to the concentration of water droplets or ice crystals in the air that make up clouds, and air temperature measures how hot or cold the air is. Each of these elements is important for understanding weather, but they do not pertain to the measurement of water vapor, which is the essence of humidity.